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Avalanche Forecast

Dec 18th, 2015–Dec 19th, 2015
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Sea To Sky.

Continued loading from forecast new snow and wind will trend the avalanche danger up over the weekend.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Sunday

Weather Forecast

Moderate southwest winds and 5-10 cm overnight for Saturday morning. Moderate southwest wind and 15-25 cm during the day Saturday. Another 15-25 cm by Sunday morning. Winds becoming light west-southwest during the day as the storm moves east and leaves another 5-8 cm. Monday should be light winds and light snow. The freezing level should remain at about 500 metres throughout the forecast period with a chance of a brief rise to around 800 metres on Sunday morning.

Avalanche Summary

Widespread loose dry activity up to size 1.5 and explosives control up to size 2.0 has been reported from Whistler Friday morning. I suspect that some pockets of wind transported snow may be easy to trigger on lee aspects. Watch for longer fracture propagations resulting in larger avalanches as the new storm snow load increases and settles into a cohesive slab.

Snowpack Summary

New storm snow was reported to be releasing very easily as loose dry above the old surface, and may be sitting on a new surface hoar layer buried on December 17th. The new snow came in a bit warmer at about -3 on top of the previous thin layer of cold snow at about -11 on Thursday, resulting in some surface slabbing and long propagations. Northerly winds transported some snow on Wednesday into soft wind slabs on lee aspects. There were some reports of easy test results between the wind slab and the old storm snow below. These new wind slabs overlie 40-50cm of storm snow from last weekend.

Avalanche Problems

Storm Slabs

New storm slabs may not bond well to the old surface of cold loose snow, wind crusts, and/or buried surface hoar.
Avoid travelling in areas that have been reverse loaded by winds.>Avoid avalanche terrain during periods of heavy loading from new snow and wind.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Loose Dry

Loose snow may slide easily on buried wind crust and or surface hoar.
Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid travelling under cliffs that are exposed to sluffing from above.>Be cautious of sluffing in steep terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2